Safety device for crane boom control



May 15, 1962 w. c. HOLMES SAFETY DEVICE FOR CRANE BOOM CONTROL 2 She ets-Sheet 1 Filed Jan. 30, 1957 INVENTOR. mum/w c. HOLMES May 15, 1962 w. c. HOLMES SAFETY DEVICE FOR CRANE BOOM CONTROL Filed Jan. 50, 1957 2 Sheets-Sheet 2 lww IN VEN TOR. 40/ 4 MM c. 1/0 M65 3,h3i,b2h Patented May 15, 1962 Free SAFETY lDlEVlQE Flllt (JEEANE BUUM CQNPCRQL William C. Holmes, 4520 W. .llefierson, lEcorse, Mich. Filed .lan. 30, 1957, Ser. No. 637,297 4- Claims. (Cl. 192-41) A boom in a power crane of conventional construction is pivotally mounted at its lower end upon the turntable of the crane and is adapted to be lowered or raised by means of a cable which is wound upon a cable drum. The rotation of the drum is controlled by a brake which may be operated by suitable means responsive to manual operation thereof.

The boom may be lowered under its own weight or the combined weight of the boom itself and a load supported thereby, and the lowering itself may be controlled by means of a brake, which in the older models of cranes is done manually. At times, however, it appears desirable to retard or regulate the lowering of the boom by means controlled by the engine of the crane.

This is desirable when the load is of relatively large weight or where special care has to be taken in lowering of the load because of its nature or the site upon which the load is to be placed. In such cases it is possible to have the cable drum coupled to the engine by a clutch which has to be operated manually.

However, there is always the danger that by oversight the operator of the crane might fail to employ the clutch when most needed for connecting the cable drum to the engine driven hoist shaft, so that as a result thereof the boom may drop down with excessive speed, damaging the load or imperiling workers in proximity of the boom. It was to prevent such an eventuality that I have devised pneumatic means which, on release of the brake, will automatically couple the engine of the crane to the cable drum.

A further object of the invention is to provide means which may be easily installed on the cranes already operated by pneumatic means without the need of any structural changes in said crane.

I shall now describe my improvement with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic presentation of a power crane of the type in which my device may be installed;

FIG. 2 is a side elevational view of the mechanism controlling the operation of the boom of the crane, the View including my device;

FIG. 3 is a perspective View of a stand, shown in fragment, and a lever mounted thereon and serving for the operation of the boom;

FIG. 4 is a diagram indicating the path of the movement of the lever in the course of its operational use;

FIG. 5 is a top View of a horizontally-disposed cylinder including a movable rod operated by pneumatic means for engagement of a clutch which forms a part/of my device.

Similar numerals refer to similar parts throughout the several views.

The drawing in FIG. 1 shows the principal elements of a power crane of the type in which my improvement may be used. The elements include a cab lit, a traction gear 11 of the crawler type, a boom 12, and a bucket 13 which is suspended from a cable and which may be lowered or raised by means of said cable.

As my device is to be employed with certain elements of the mechanism for raising and lowering of the boom,

1 will first describe such pertinent members of the mechanism as may be needed for the understanding of the operation of my device.

The boom is mounted pivotally at its lower end by means of a pin in a bracket 16. The cable 14 which controls the movement of the boom is attached to the upper end thereof, passes over a pulley 18 at the upper end of a stationary beam 19 which is mounted upon a turntable 17 of the crane, and is wound upon a drum 20 which is also mounted on said turntable.

Co-axially mounted with the drum on a shaft 21 is a gear wheel 22. The gear wheel is in mesh with an idler 23, and by means of said idler is in engagement with a pinion '77 mounted upon brake wheel 24 journaled on a shaft S known as a swing shaft.

Mounted upon said shaft S is a brake wheel 24, and encircling said wheel is a brake band 25 which at one end is anchored to a stationary member 26 rising from the surface of the turntable. At the opposite end the brake band 25 is connected to a horizontal rod 28. A spring 29, coiled about the rod, bears at one end against a stationary member 30 and keeps the band in a tight frictional engagement with the portion of said brake wheel M. A ratchet wheel 31, secured to brake wheel 24 is loosely mounted upon the same shaft which carries the brake wheel, is controlled by a pawl 32. Midway its length pawl is fulcrumed upon a pin 27 and is provided, at the end remote from said ratchet wheel, with a weight 33, and the object of the weight being to keep the pawl normally in engagement with the teeth of said ratchet wheel to prevent rotation thereof.

As at times it is desirable to have the lowering of the boom controlled by the engine of the crane, a special mechanism is used for that purpose. It includes a sprocket wheel 34 loosely journaled and mounted upon one end of a hoist shaft H which, through intermediate means, is driven by the engine of the crane. Connected to said wheel by means of a driving chain 35 is another sprocket wheel 36 which is mounted upon shaft 37. A gear wheel 38, mounted on the same shaft, is in mesh with gear wheel 22 controlling the cable drum.

A clutch 39, a long lever 46 is slidably keyed to hoist shaft H and is connected to said clutch, serves as a means of coupling the hoist shaft driven by the engine to the sprocket wheel 34 in turn connected by chain 35, sprocket gear 36, and gear wheel 38 to gear wheel 22. The lever, which is disposed diametrically with respect to the clutch 39, is hinged at one end at 78, to a stationary member 4-1 on the stationary beam 19, while the opposite end of the lever terminates with a downwardlyturned handle 42. Coiled spring '71, FIG. 5, is anchored at 7d to stationary member 69 and at its opposite end is joined to lever 40 normally biasing the clutch 39 into a disengaged position with respect to the sprocket wheel 34. Thus power driven hoist shaft H is disconnected from cable drum 29.

Located at the front end of the turntable is a stand 43, and mounted thereon is a lever 44 terminating at the upper end with a ball 45, this being of a size to fit into the palm of the operator of the crane. Adjoining the ball is a push button it; in an electric circuit which includes switch means within the stand and solenoid means under the turntable.

The drawing in FIG. 2 shows a single solenoid 47 which controls a valve 48 upon a pipe 48a shown in fragment and leading from the source of supply of compressed air, such as a compressor. Extending from the valve is a pipe 49 which leads to a union 50, while another short pipe 51 leads from the same union to a cylinder 52 from which air, under pressure, is adapted to actuate a rod 53. The rod extends slidingly from the cylinder and is pivotally connected at its outer end to the lower end of a vertically-disposed lever 54. The lever, which is pivotally secured at its upper end to the stationary member 26, as shown at 55, bears at its midportion against a cap 56 which is secured to one end of 3 said rod 28 and which is connected to one end of the brake band 25.

Another pipe, 64, leads from the union 50 to a cylinder 65 which is mounted on a bracket 66, the latter being secured to .a stationary brace 67 of the framework of the crane upon said turntable. The cylinder, best shown in FIG. 5, is kept in place by means of a band 68 which is carried by the bracket, the latter being in a radial relation to said cylinder. One end of the cylinder is provided with a radially-extending bar 69, and connected thereto, by means of an eyelet 70, is one end of a coiled spring 71, while its other end is hooked to the lever 40, a shown at 72.

The opposite end of the cylinder is provided with an axial opening through which a sliding rod 73 extends outwardly. It will be understood that the rod 73 is normally kept in a retracted position within said cylinder by suitable spring means, but that it is adapted to be pushed outwardly against said lever 40 by compressed air admitted to the cylinder through said pipe 64.

The drawings also show a clutch 63 slid-ably keyed on one end of the swing shaft S of the crane which is also controlled by pneumatic means. These include a cylinder 58 which is mounted in a housing bracket 59. A red extending from the cylinder and adapted to be actuated by air pressure is connected to the lower end of a vertical lever 60 which is fulcrumed at 61 and which terminates at its upper end with a fork 62. It is this fork that is adapted to shift the clutch 63 from its engaged to its disengaged position with respect to brake wheel 24, or vice versa.

Air under pressure is applied to the cylinder through a pipe 57 controlled by means of another solenoid valve which is not shown. The solenoid valve operates only when the boom is to be raised.

As these details pertaining to the operation of the clutch 63 are well known and are no part of the applicants invention, no further particulars on the subject are deemed necessary herein.

It will be noted that, as before stated herein, said lever 40 serves as a means of moving the clutch member 39 shown in FIG. 2 between engaged and disengaged position relative to sprocket wheel 34. A pipe 74, extending laterally from said pipe 64, leads to a vertical cylinder 75 on the upper surface of the turntable 17 and contains a rod 76 adapted to be pushed upwardly by air pressure against the lower end of weight 33 at one end of the fulcrumed pawl 32.

I shall now describe the working of my device in the course of the operation of the boom.

It will be assumed that the boom is up and that the clutch 39 due to spring 71 and lever 40 is in its normal disengaged position relative to sprocket wheel '34 on the end of the hoist shaft. Now, should the operator desire to lower the boom, he can do so by means of the lever 44, which in a well-known crane now in use has to be swung from its neutral position, indicated by numeral 45a in the diagram shown in FIG. 4, to the left to the position marked 45b. At the same time as the operator will grasp the ball 45 at the upper end of the lever, he will depress the switch button 46. The button and an auxiliary switch not shown will close an electric circuit, energizing the solenoid 47. The latter will open the valve '48 admitting air under pressure to cylinder 52. As a result thereof, the rod 53 will swing the lever 54 from its pivotal connection at 55 against the cap 56 on the rod 28, and, overcoming the tension of the coiled spring 29, will loosen the brake band on the brake wheel 24.

Simultaneously, air under pressure is admitted to the cylinder 75 located under the weight 33 so that the rod 76 will rise from the cylinder and lift said weight, thus disengaging the pawl 32 from the teeth of the ratchet wheel 31. Also simultaneously, air under pressure is delivered through pipe 64 to the cylinder 65. Here the rod 73 is pushed out by air pressure, overcoming the tension of spring 71. The rod, extending outwardly from the cylinder 65, bears against the lever 40 and moves it outwardly from said cylinder, causing it to shift the clutch 39 on the hoist shaft H from its disengaged to its engaged position relative to sprocket gear 34. This serves to couple the power of the engine of the crane to the cable drum or boom drum 20. As a result thereof, the unwinding of the cable is retarded and the speed of the unwinding may be controlled by the engine which is capable of a wide range of variable speeds.

Upon return of the lever 44 to the neutral position indicated by numeral 45a in FIG. 5 and on release of the switch button 46, the current which energizes the solenoid 47 will be cut off and the valve 48 which is controlled by said solenoid will be closed. As a result thereof, the coiled spring 71 will pull the lever 40 towards the cylinder 65, the rod 73 will be withdrawn into the cylinder under the tension of a spring within said cylinder, and the clutch 39 will be shifted by said lever '46 back to its disengaged position, uncoupling the engine from the boom hoist drum.

The closing of the valve 48 will also cut off the supply of air under pressure from the cylinder 52 and cylinder 75, causing the respective mechanisms operated by rods extending from said drums or cylinders to return to their normal positions.

More specifically, rod 73 will be withdrawn into the cylinder 65 by spring means located within said cylinder, permitting the coil spring 71 to draw the lever 46 towards said cylinder. As a result thereof, the lever 40 will shift the clutch 39 on the hoist shaft from its engaged to its disengaged position, thus disconnecting said shaft H which is driven by the engine of the crane from the cable drum 20.

As my device operates only at the time when the boom is to be lowered, the description of the functions of the respective mechanisms operated by the last-named cylinders for raising the boom does not appear necessary in this disclosure.

It will be understood that the forms and locations of the air-controlled means pertaining to my device may be varied in form and their locations with respect to each other or the pertinent elements of the crane without thereby departing beyond the range of the invention disclosed herein. It will be also understood that any other fluid medium than compressed air may be used to actuate my device and the elements working in combination therewith.

What I, therefore, wish to claim is as follows:

1. In a crane, a power driven hoist shaft, a rotary cable drum, a brake to control the rotation of said drum, a normally disengaged clutch upon said hoist shaft and movable thereon from disengaged to engaged position to couple the hoist shaft to the drum, a lever pivoted at one end to a stationary support and intermediate its ends secured to said clutch, spring means secured to a stationary support and joined to and acting upon the lever to hold the clutch in its disengaged position, a cylinder upon a stationary support including a reciprocal piston rod extending axially into contact with the lever at substantially right angles thereto, a pipe leading to the cylinder to supply thereinto a fluid medium under pressure to push the rod outwardly against said lever, for moving said lever and the connected clutch to engaged position, a power means adapted to release the brake, a manual control switch means, a valve connected to a source of fluid under pressure and having an outlet connected to said pipe and to said power means, a control means for opening said valve connected to said manual control switch so that on actuation of said switch said valve is opened actuating said power means, releasing said brake and simultaneously delivering fluid to said cylinder to shift said lever and connected clutch to engaged position relative to the cable drum.

2. In the crane of claim 1, said brake including a power driven swing shaft, a brake drum loosely journaled thereon, a gear train interconnecting said brake drum and said cable drum, and a resiliently mounted brake band normally engaging said brake drum retaining said cable drum against rotation.

3. In the crane of claim 1, the connection between said hoist shaft clutch when in engaged position relative to said cable drum including a sprocket gear train connected to said cable drum in driven relation, said latter clutch when moved by said lever to engaged position, being in operative engagement with said gear train.

4. In the crane of claim 1, said brake including a power driven swing shaft, a brake drum loosely journaled thereon, a gear train interconnecting said brake drum and said cable drum, a normally disengaged clutch as- References Cited in the file of this patent UNITED STATES PATENTS 1,979,780 Turney Nov. 6, 1934 2,098,342 Knutzen Nov. 9, 1937 2,445,116 Huston July 13, 1948 2,506,842 Rockwell May 9, 1950 2,590,172 Guier et al Mar. 25, 1952 2,693,341 Fox Nov. 2, 1954 

